Submitted to: Journal of Chromatography
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/1997
Publication Date: N/A
Interpretive Summary: Antioxidants are useful agricultural products and exist in nature as complex mixtures. Because of the lack of suitable analytical methods for antioxidant assays, good analytical techniques are needed to assess the vitamin-like substances in vegetable oils. A new analytical method has been developed. Antioxidant contents of genetically modified vegetable oils were determined and their compositions were compared among different varieties of oilseeds. The technique can be used by oilseed growers and food technologists for the evaluation of antioxidants in plants and foods. Oilseed researchers can use the analytical data to improve the quality and stability of vegetable oils by genetic modifications of oilseeds.
Technical Abstract: The retention behavior and separation characteristics of five natural antioxidants alpha-, Beta-, gamma-, delta-, and zeta-tocopherols and their acetyl derivatives were studied by reversed-phase high-performance liquid chromatography (HPLC) fluorescence detection. Investigated stationary phases included an octadecyl polyvinyl alcohol (ODPVA) column, several octadecylsilica (ODS) columns, and a pentafluorophenylsilica column. Mobile phases comprised methanol (or acetonitrile) and water at variable proportions. Separation factors for Beta- and gamma-tocopherol isomers and capacity factors of the five tocopherols were determined under various conditions. The Beta- and gamma-tocopherols were separable on ODPVA but not on ODS. However, the Beta-gamma pair was resolved with the latter column only as their ester derivatives. HPLC with mobile phases containing alkanols with carbon atoms greater than two favored the separation of the Beta-gamma pair on ODS and yielded results diametrically different but complementary with those obtained with the ODPVA phase. The combined effects of mobile phases, stationary phases and antioxidant structures on component separations were delineated.